A microgrid is a localized grouping of electricity generation, energy storage, and loads that normally operates connected to a traditional centralized grid (macrogrid) via a point of common coupling (PCC). This single point of common coupling with the macrogrid can be disconnected, islanding the microgrid. Microgrids are part of the structure for so called distributed generation (DG) aiming at producing electrical power locally from many small energy sources.
A microgrid (in grid connected mode, i.e. connected to the macrogrid) supplies the optimized or maximum power outputs from the connected DG sites and the rest of the power is supplied by the macrogrid. The microgrid is connected to the macrogrid at a PCC through a controllable switch. This grid connection is lost during grid fault and microgrid is islanded.
U.S. Pat. No. 8,447,435 generally discloses connection between and control of a plurality of microgrids with a PCC to the macrogrid.
To avoid islanding, multiple PCC can be used. Multiple PCC connection may provide improved grid reliability but power management, protection, power flow control, stability and islanding detection (at one PCC point) become more complex.